@Haider4u 

There's a few things we have to look at... Signal Strength of your wireless client, RX/TX, and band they are sitting on duting these times.

If you goto the client list, you can click on the 3 dots at the right.  Enable Customized Columns:

Then check channel, wireless connection, signal, RX/TX.

Post a screen shot of the client info here.  

  @Haider4u 

thanks for the screenshots... out of that list, which client are you testing with?  

There is an AC client at 6mpbs RX rate, which is super low.  

2.4ghz clients RX TX speeds are low anyway, due to the band.  

Run the WiFi opitmization and see if it changes any channels.  

You can take those speeds and cut them 75% off of it and you will guesstimate the real time speeds the client will make.